The present invention relates to an assembly with a planetary gear train which can be used in a motor vehicle. The planetary gear train has the following elements: a sun gear, a planet carrier with planetary gears configured for rotation about the sun gear, and a ring gear surrounding the planetary gears. All three elements are typically able to rotate, unless one element is locked in place.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
It is known to use a planetary gear train for coupling an electric machine with an combustion engine in a motor vehicle. The planetary gear train enables different gear ratios between the electric machine and the combustion engine. Optionally, other units, for example a compressor for an air-conditioning system of the motor vehicle, can be additionally provided. The compressor may hereby be coupled with the electric machine via a belt drive, wherein the belt drive is used at the same time to for couple the electric machine to the sun gear of the planetary gear train.
Because the electric machine and the combustion engine should be able to operate independently in some operating modes, it is known to arrange in the planetary gear train an overrunning clutch between two predetermined (selected) elements. If, for example, the crankshaft of the combustion engine is coupled with the planet carrier and the sun gear is coupled with a pulley for the belt drive which implements coupling with the electric machine, then the sun gear and the planet carrier are the two selected elements which are coupled with each other via an overrunning clutch. The transmission direction of the overrunning clutch hereby runs from the planet carrier to the sun gear, i.e. from the crankshaft to the pulley and the belt and hence to the rotor of the electric machine. The electric machine can then overtake the combustion engine, i.e. rotate with a higher rotation speed than the rotation speed of the combustion engine, multiplied with the gear ratio of the gear.
However, an overrunning clutch also has disadvantages. During the operation of the combustion engine, the rotation speed can vary due to excitations from a finite number of combustion chambers. As a result, the overrunning clutch may then continuously briefly open and close. This increases the wear of the overrunning clutch. Moreover, this operation of the overrunning clutch may also produce irritating noise.
It would therefore be desirable and advantageous to obviate prior art shortcomings and to provide an improved assembly with a planetary gear train and an overrunning clutch between two selected elements of the planetary gear train.